1. Field of the Invention
The present invention relates to a vehicle stop control device and a vehicle stop control method by adjusting a braking force with respective to wheels to stop the vehicle.
2. Description of Related Art
Generally, when the vehicle is stopped by applying the braking force to the wheels of the vehicle, a so-called “swing-back” occurs, in which after a center of gravity of the vehicle body is moved forward before the vehicle is stopped, the center of gravity of the vehicle is moved backward by a force of restoration of the vehicle suspension, or the like at the time of the stopping of the vehicle. This swing-back causes displeasure to passengers in the vehicle. Therefore, for example, JP-A-H1-164656 or JP-A-H11-208439 has proposed a vehicle stop control device which adjusts the braking force or driving force automatically in the vehicle such that deceleration of the vehicle becomes almost “zero” immediately before the vehicle is stopped in order to suppress the swing-back at the stopping of the vehicle, even if the driver of the vehicle does not operate an accelerator pedal or a brake pedal.
In the stop control device of JP-A-H1-164656 (hereinafter, also referred to as “first conventional device”), a liquid pressure within a master cylinder (also referred to as “MC pressure”) is detected based on a detected signal which is output from a liquid pressure-sensor according to a depression amount of the brake pedal of the driver, and assumes a reference deceleration which is greater as the MC pressure is higher. Furthermore, in the first conventional device, in the case where the driver depresses the brake pedal, when an actual deceleration of the vehicle is greater than the reference deceleration, it is determined that a road surface on which the vehicle is driving is an ascent road, and braking control for the ascent road is performed. As a result, the swing-back is suppressed when the vehicle is stopped even when the vehicle is driving on the ascent road.
In the stop control device of JP-A-H11-208439 (hereinafter, also referred to as “the second conventional device”), it is determined whether the road surface which the vehicle is driving is any one of a horizontal road, an ascent road or a descent road based on a detected signal output from an inclination angle detection sensor such as an acceleration sensor, etc. Further, in the second conventional device, when it is determined that the road surface which the vehicle is driving is the ascent road, the braking force which is applied to the respective wheel of the vehicle is released during a predetermined time after the vehicle is stopped, and a driving force, which is of an extent that the backward movement of the vehicle can be suppressed, is transferred to the wheels of the vehicle. As a result, the swing-back is suppressed when the vehicle is stopped, and the backward movement of the vehicle is suppressed.
However, recently, there has been a demand for the miniaturization and cost reduction of a vehicle-mounted brake actuator. Accordingly, there is a possibility that brake actuators not having a liquid pressure sensor or an acceleration sensor are mounted on a vehicle. In each conventional stop control device, the brake actuator not having the liquid pressure sensor or the acceleration sensor cannot be controlled properly since it cannot be determined whether the road surface which the vehicle is driving is an ascent road or a descent road. Therefore, the braking force of the vehicle cannot be adjusted properly when the road surface is the ascent road. As a result, there is a concern that the effect of suppressing the swing-back when stopping the vehicle cannot be obtained. Thus, technical developments are needed that can detect whether the road surface is an ascent road without using the detected signal output from the liquid pressure sensor or the acceleration sensor. Herein, “the ascent road” means that the road has a slope (an inclination angle) on which the vehicle is caused to move backward when braking force is not applied to the vehicle.